Cross-linked multifunctional binder in situ tuning solid electrolyte interface for silicon anodes in lithium ion batteries.

Silicon is considered as the most promising anode material for high performance lithium-ion batteries due to its high theoretical specific capacity and low working potential. However, severe volume expansion problems existing during the process of (de)intercalation which seriously hinders its commercial progress. Binder can firmly adhere silicon and conductive agent to the current collector to maintain the integrity of the electrode structure, thereby effectively alleviating the silicon volume expansion and realizing lithium-ion batteries with high electrochemical performance. In this paper, citric acid (CA) and carboxymethyl cellulose (CMC) are adopted to construct a covalently crosslinked CA@CMC binder by an easy-to-scale-up esterification treatment. The Si@CA@CMC-1 electrode material shows an impressive initial coulombic efficiency (ICE) at 82.1% and after 510 cycles at 0.5 A/g, its specific capacity is still higher than commercial graphite. The excellent electrochemical performance of Si@CA@CMC-1 can be attributed to the ester bonds formed among CA@CMC binder and silicon particles. Importantly, by decoupling in situ EIS combining XPS at different cycles, it can be further proved that the CA@CMC binder can tune the component of SEI which provide a new-route to optimize the performance of silicon.

An in situ thermal cross-linking binder for silicon-based lithium ion battery.

Silicon has been regarded as one of the most promising anode materials for lithium-ion batteries (LIBs) due to its highest specific capacity and low (de)lithiation potential, however, the development of practical applications for silicon are still hindered by devastating volume expansion and low conductance. Herein, we have proposed an in situ thermally cross-linked water-soluble PA@PAA binder for silicon-based LIBs to construct dynamic cross-linking network. Specifically, ester bonds between -P-OH in phytic acid (PA) and -COOH in PAA, which are generated by thermal coupling, are designed to synergize with hydrogen bonds between the PA@PAA binder and silicon particles to dissipate the high mechanical stresses, which is verified by theoretical calculation. GO is further adopted to protect silicon particles from immediate contact with electrolyte to improve initial coulombic efficiency (ICE). A range of heat treatment temperatures is explored to optimize the previous process conditions and the optimum electrochemical performance is provided by Si@PA@PAA-220 electrodes with high reversible specific capacity of 1322.1 mAh/g at a current density of 0.5A/g after 510 cycles. Characterization has also revealed that PA@PAA is involved in electrochemical process and tunes the ratio of organic (LixPFy/LixPOyFZ)-inorganic (LiF) to consolidate solid electrolyte interface (SEI) during cycles. In brief, this applicable fascial in situ strategy can effectively improve the stability of silicon anodes for high energy density lithium-ion batteries.